Aim: The aim of this thesis is to investigate team effectiveness in the field of construction. With this study, influential factors on team collaboration between different companies and within teams will be defined. By defining these factors, project managers of comparable project-based integrated design teams can improve the team collaboration within the project team and with that optimize their team’s effectiveness. The research focuses on a big complex building project, which will be used as a transportation hub, in the Netherlands. Research question: What are key factors which influence team collaboration of a project-based integrated design team in context of a large-scale complex building project, influenced by fast growth, different cultures and a changing scope? Methodology: The factors are explored by conducting a single case study research. The starting point was a literature study towards team effectiveness. The outcome of this study was used as input for the case study research. The case study was used to collect data, the data was generated by conducting semistructured interviews. After these interviews were conducted, observations, off the record conversations and inspection of restricted documents were used to discuss and validate conclusions. Findings: The literature research concluded in the backbone of this research. The IMOI model of Ilgen et al. (2005), structure the inputs, mediators and outcomes of the team’s effectiveness. The model is used to determine different factors that could influence the team collaboration. The case study research determined three events which are important for the further course of the project. Due to a lack of management during these events, the client in combination with leading members of the team had to overrule the management layer. The events; assembling the team, collaboration during the project and involving team members have to be managed with both organizational and interpersonal skills. Limitations of the research: It is a qualitative research; therefore, the research is always subject to biased opinions and interpretations of the data. Besides that, the research is conducted on only one case and therefore not automatically representative for all comparable cases. However, the factors resulting from this study need to be kept in mind, due to the fact that it will always be factors that influence the team collaboration, not said that they have to be the most influential for every comparable project-based integrated design team. Practical implications: The research addresses factors that affect the team collaboration of a project-based integrated design team. These factors should be taken into account when starting a comparable project team. Even though the case study of this research concluded with these factors, it is not excluded that there are more factors that influence the team collaboration of a project-based integrated design team. Therefore, more studies should be conducted in this area of research. Scientific relevance: There are a lot of studies conducted towards the team effectiveness of composed teams, however, more research is needed to define the factors that influence the team collaboration of a projectbased team. This research could be used as a starting point for further research, while it is one of the first studies conducted on a project-based team of this size and complexity, subjected to designing a big complex building project. Keywords: Project-based integrated design team, team collaboration, team effectiveness, project management, IMOI framework.